The immune system is that complex organization of cells, chemical reactions, tissues and organs that help the body ward off some forms of disease, especially germs and pathogenic microorganisms.
Physical activity affects the way the immune system works, as does nutrition and stress. With physical activity and exercise, different volumes and intensities of exercise can either enhance immunity or degrade it.
Effects of Exercise on the Immune System
- As a general rule, high-intensity and volume exercise tends to degrade antibody production in the immune system, while regular, moderate exercise intensity tends to enhance the immune function. Whether your immunity is inhibited enough to make you more susceptible to diseases depends on your individual circumstances.
- The beneficial impact of moderate exercise may be related to its anti-inflammatory effects. In this context, the beneficial effects of endurance exercise are well-known, while the effect of resistance and weight training is not well-known.
- Prolonged, intense exercise may induce negative health consequences, many of which may be mediated by chronic stress as a consequence of overreaching and overtraining. (Think of overreaching as a short-term excessive training load, and overtraining as a longer-term, chronic, and less easily reversed excessive training load).
- While some evidence exists that exercise lowers the risk of colorectal and breast cancer, and helps in cancer recovery, the exact mechanism, and how immunity is involved, is not clear.
- Upper respiratory tract infections (URTI) are a common infection and illness in heavy training athletes, especially endurance athletes.
- Each person's immune system variability, training program competence, exercise capacity, non-training stress factors, and stress tolerance are likely to explain the different vulnerabilities of athletes to illness.
- Regular, moderate exercise could be an important factor in ameliorating the adverse health effects of non-exercise chronic stress. ('Moderate' exercise is less than 75% of maximum heart rate.)
How to Train to Avoid Negative Immune System Effects
- Start with a program of low to moderate volume and intensity.
- Employ a gradual and periodized increase in training volume and intensity.
- Avoid excessively heavy training loads that lead to exhaustion and overreaching.
- Include cross-training days to vary physiological and psychological stresses.
- Formally monitor rest and recovery, including programs for identifying deterioration of performance, and psychological and physical stress.
- Ensure superior hygiene practices.
Supplements for Immune System Enhancement
Adequate carbohydrate intake in athletes suppresses the hormone cortisol, produced during heavy training, and which is known to suppress the immune system. In addition, markers of inflammation are reduced with sufficient carbohydrate.
Nutritional supplements, including vitamins C and E and many others, have shown little promise in promoting immunity. More recently, the polyphenol nutrients in plants have shown some promise in boosting immunity. Here is a summary of supplements that have been scientifically tested for effect on the immune system.
- Vitamin E - not effective, may be pro-oxidative
- Vitamin C - not effective
- Multivitamins - not effective, balanced diet sufficient
- Glutamine - not recommended, no need
- Branched-chain amino acids - as above, no need
- Carbohydrate - recommended, up to 60 gm/hour
- Bovine colostrums - under evaluation, mixed results
- Probiotics - mixed results
- Omega-3 fats, fish oils - no effect
- Beta glucan - not recommended at this time
- Ginseng, echinacea - not recommended, no effect
- Quercetin - recommended, positive results in several studies
Walsh NP, Gleeson M, Shephard RJ, Gleeson M, et al. Position statement. Part one: Immune function and exercise. Exerc Immunol Rev. 2011;17:6-63.
Walsh NP, Gleeson M, Pyne DB, Nieman DC, at al. Position statement. Part two: Maintaining immune health. Exerc Immunol Rev. 2011;17:64-103.